A materials physics perspective on structure–processing–function relations in blends of organic semiconductors

During the past 30 years of research in organic electronics, the development of mechanistic understanding of important structure–processing–performance interrelationships has been slowly but steadily growing. Nevertheless, especially if blends are used in the active device layer, the development of new materials and device fabrication still predominantly relies on time-consuming trial-and-error procedures. In this Review, we demonstrate that well-established models, rooted in classical materials science and the thermodynamics of mixtures, can provide quantitative frameworks to guide material and process design. We provide, from a materials physics perspective, a concise and accessible overview on the relation between fundamental thermodynamic and kinetic principles relevant to (solution) processing, active layer morphology and stability of organic electronic devices based on blends by means of illustrative examples from organic photovoltaics. We aim to address a wide audience, including synthetic chemists, materials scientists, device engineers and beyond.